This invention relates to strong, stiff, tough glass-filled olefin polymers and particularly to glass-filled blends of high crystalline, high tacticity, propylene polymers with plastomer ethylene-lower alkene copolymers, which are both tough and strong.
Glass-filled polyolefins, including high crystalline propylene polymers, are well known in the art and, typically, are produced to increase the strength or stiffness of the base polymer. However, a common trade-off for such increase in strength or stiffness is a loss of toughness and elongation at break. Toughness may be enhanced by incorporation of less crystalline or rubbery polymers into a glass-filled polymer blend. However, incorporation of such less crystalline or rubbery materials generally will decrease the stiffness and strength properties of the filled resin.
Glass-filled polypropylenes have advantageous properties such as high strength, stiffness, chemical resistance, low specific gravity, and low cost relative to typical glass-filled engineering resins. Possible applications of such glass-filled polypropylenes include appliances, hot water plumbing and irrigation systems, and automotive uses. A glass-filled high crystalline polypropylene has substantially increased strength and stiffness compared to conventional glass-filled isotactic polypropylenes. However, as noted above, such increase in stiffness or strength normally is at the expense of toughness or impact properties. An unblended high crystalline (high stiffness) polypropylene generally is more brittle and more notch sensitive than conventional polypropylene. A glass-filled high crystalline polypropylene also shows relatively poor impact and toughness properties. The need for a tough glass-filled polypropylene especially is desired for higher melt flow rate polymers which permit glass-filled polymers to be molded into large and complex parts.
Modification of polypropylene with plastomers has been described by Yu, Society of Plastics Engineers, Conference Proceedings, ANTEC 95 (1995), pp. 2374-2385. Cheng, Erderly, and Yu described plastomer and polypropylene blends for fiber and nonwoven applications in Society of Plastics Engineers, Conference Proceedings, ANTEC 95 (1995), pp. 2386-2392. Neither of these papers describe a glass-filled, high crystallinity polypropylene blended with a plastomer.
Hojabr and Boocock, Society of Plastics Engineers, Conference Proceedings, ANTEC 95 (1995), pp. 3620-3627, describe using polyolefin coupling agents in glass-filled polyolefins.
Glass-filled polyolefins, such as glass-filled polypropylenes, have been widely described. Use of a maleic acid- or anhydride-grafted polymer to improve adherence between a polypropylene and glass fiber is described in U.S. Pat. Nos. 4,599,385 and 4,673,210. Use of an organic peroxide to shorten molecular chains together with a modified polypropylene in a glass fiber-containing composition is described in U.S. Pat. No. 5,264,174. Modification of a polymer used in a glass-filled polypropylene using a unsaturated peroxide is shown in U.S. Pat. No. 5,447,985.
Incorporation of an ethylene-propylene copolymer in a glass fiber-containing composition is described in U.S. Pat. No. 4,983,647, while U.S. Pat. No. 4,621,115 describes use of a ethylene-propylene copolymer modified with itaconic anhydride in a glass-filled polypropylene. Inclusion of polymer reinforcing materials into a glass-filled polypropylene have been shown in U.S. Pat. No. 5,082,889 (polyethylene and an aromatic hydrocarbon resin); U.S. Pat. No. 5,030,682 (polybutene-1); U.S. Pat. No. 4,990,554 (ethylene-propylene random copolymer); U.S. Pat. No. 5,324,755 (styrenic polymer); U.S. Pat. No. 5,286,776 (styrenic hydrogenated block copolymer and a noncrystalline ethylene-.alpha.-olefin copolymer); and U.S. Pat. No. 5,208,081 (rubber-like copolymer).
U.S. Pat. No. 5,238,989 describes a glass-filled polypropylene composition containing a modified polypropylene obtained by heating and melting a mixture of an unsaturated acid, an unsaturated silane and an organic peroxide to a crystalline polypropylene.
Use of silanes to size glass fibers in a glass-filled polypropylene have been described in U.S. Pat. Nos. 5,013,771, 5,300,547, 5,308,893, 5,376,701, and 5,437,928. High melt flow polypropylene used in a glass-filled polypropylene was shown in U.S. Pat. No. 4,997,875.
Polypropylenes having high tacticity have been described in U.S. Pat. No. 5,412,020 which have been blended with a block copolymer and a thermoplastic elastomer and may contain an inorganic filler.
U.S. Pat. No. 5,218,052 describes a high isotactic polypropylene having increased stiffness and a broadened molecular weight distribution.
There is a need for a glass-filled polypropylene which has a good balance between strength and toughness properties. The present invention combines a high crystalline (high isotacticity) propylene polymer with a broadened molecular weight distribution with a specified ethylene copolymer plastomer in a glass-filled product to produce a material which shows both good strength, stiffness, and toughness properties and satisfies commercial requirements for products. Such a product would be advantageous for many applications such as hot water plumbing, automotive instrument panels, electrical connectors, pump housings, valves, water tanks, sprinkler heads and the like.